A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air moves into the engine through the fan section. Airfoil arrays in the compressor section rotate to compress the air, which is then mixed with fuel and combusted in the combustor section. The products of combustion are expanded to rotatably drive airfoil arrays in the turbine section. Rotating the airfoil arrays in the turbine section drives rotation of the fan and compressor sections.
Gas turbine engines may have various gas-flow streams that may be kept separate from one another. The gas-flow streams may be separated by various components. Higher pressure gaspath air may tend to leak between airfoil arrays into lower pressure gaspaths. The internal engine environment is exposed to temperature extremes and other harsh environmental conditions, which may affect the integrity of the components separating different gas-flow streams. The loss of secondary flow air into the gas-path of a turbine has a negative effect on engine fuel burn, performance/efficiency, and component life.